1. Field of the Invention
This invention relates to an orthodontic device comprising an upper jaw thrust plate and a lower jaw thrust plate, which are connected to the teeth and used for a sagittal treatment effected by a cooperation between activating rods and slideways in the front teeth region so as to displace the jaws relative to each other.
2. Description of the Prior Art
Such thrust plates serve to correct a condition which is described as supraocclusion and in which the lower jaw is excessively set back from the upper jaw. The thrust plates consist of an upper jaw thrust plate and a lower jaw thrust plate. Two activating rods are embedded in the upper jaw thrust plate and bear under initial stress on an inclined planar surface provided on the lower jaw thrust plate adjacent to the front teeth and during an opening and closing of the jaws exert a force which tends to correct the sagittal setback of the lower jaw. This action requires the dental arches of the upper and lower jaws to be adjusted relative to each other in the transversal direction so that the treatment for correcting supraocclusion must be preceded by a treatment taking about 11/2 years. The subsequent treatment for adjusting the supraocclusion or subocclusion, the opposite condition, takes additional 11/2 years so that the total treatment can only be effected as long as a growth, i.e., a rearrangement of muscles, is taking place so that there is a change of the articulated joints. Because the treatment cannot begin before the temporary teeth have been replaced and cannot be performed as long as there is growth, the success of the treatment depends highly on growth, which takes place only for a limited time, which cannot be exactly predicted.
An additional difficulty arising in the manufacture of the known devices resides in that the rods which slide on the inclined planar surface must be embedded in the thrust plate to extend absolutely parallel to the plane of the surface because an additional torque will otherwise be exerted on a jaw arch. On the other hand, the inclined planar surface of the lower jaw thrust plate must be parallel to the activating rods and must be arranged at such an angle that a forward thrust for a sagittal correction of the lower jaw is produced.